1. Field of the Invention
The present invention relates to a liquid discharge head which discharges a liquid.
2. Description of the Related Art
Heretofore, a liquid discharge head has been configured to discharge a liquid in a direction vertical to the surface of the head on which a heating resistor is disposed, and the head has been put to practical use. In such a liquid discharge head, as shown in FIG. 7A, in general, a liquid supply port 302 is rectangular as viewed from an upper surface of a head substrate 301, and liquid discharge ports 303 are linearly arranged as rows of discharge ports on opposite sides of the liquid supply port. It is to be noted that the arranged rows of liquid discharge ports 303 open at a discharge port open surface 305. FIG. 7B is a sectional view cut along the 7B-7B line of FIG. 7A. As shown in the drawing, heating resistors (hereinafter referred to as the heaters) 304 are arranged so as to face the liquid discharge ports 303, and the heaters generate thermal energy as discharge energy to discharge the liquid.
However, if the heaters 304 are highly densely arranged, it is difficult to linearly arrange the liquid discharge ports 303 as described above. This is because there are dimensional restrictions due to heater sizes and bore diameters of the liquid discharge ports 303. Therefore, instead of linearly arranging the liquid discharge ports 303 as the rows at the discharge port open surface 305 (one-dimensional arrangement), a method (two-dimensional arrangement) is proposed. In this method, the heaters 304 and the liquid discharge ports 303 are arranged non-linearly, for example, in a staggered arrangement in a plane of the discharge port open surface 305.
However, if an electric connecting portion is disposed on a front surface of the head substrate 301 (on a side provided with the liquid discharge ports) of the head substrate 301, a protruding portion is necessarily formed. As a constitution which does not have any protruding portion, it is considered that a back surface of the head substrate 301 (the surface on a side opposite to the surface provided with the liquid discharge ports) is electrically bonded. Therefore, Japanese Patent Application Laid-Open No. S61-016862 discusses that a penetrating wiring is disposed so as to penetrate the head substrate 301 from the front surface to the back surface of the substrate and that the back surface of the head substrate 301 is connected to an external wiring.
However, a driving element which allows the heaters 304 to generate heat is disposed adjacent to the heaters 304. In consequence, the wirings for driving can be reduced, but it is difficult to draw around wirings of a logic circuit which drives the driving element. Therefore, a wiring region needs to be secured. For this purpose, when the liquid discharge ports 303 (or the heaters 304) are two-dimensionally arranged, a size of the head substrate sometimes increases.
Moreover, when a liquid path extends from the liquid supply port to the liquid discharge port through a liquid chamber where the heater is disposed, the path is halfway separated so as to supply the liquid from one liquid supply port to two liquid discharge ports. In this structure, a length difference is made between the liquid paths extending to two liquid discharge ports owing to a manufacturing error. A fluctuation might be generated in discharge performances from the individual liquid discharge ports, depending on this difference.